FIREFIGHTERS have boosted their resources as strong winds continue to fan a bushfire in the Blue Mountains, west of Sydney.
A blaze at Leura, which has been burning since yesterday afternoon, has now scorched 5ha, Rural Fire Service spokesman Joel Kursawe said.
More trucks and crews had been sent to battle the fire, the cause of which is unknown, he said.
About 35 fire trucks are on the scene along with 145 firefighters and three helicopters.
"We do have a number of trucks and crews positioned behind houses in and around Olympian Parade to engage in property protection if required," Mr Kursawe told AAP.
"We don't have a threat to houses at the moment but we have adequate crews there to implement that should the need arise."
Winds have increased from 40km/h to 59km/h and are expected to get worse.
"By 3.30pm this afternoon were are predicting of gusts of maybe 75km/h," he said.
"We are continuing to work to bring the fire under control. These winds are obviously making it very hard for us and also making it very hard for the aircraft to work in high winds."
Mr Kursawe said it was possible homes could come under threat later today.
In a separate incident, a grass fire at Menangle Park near Campbelltown has closed the northbound lanes of the Hume Highway.
About 10 fire trucks and 20 crews are working to extinguish that blaze, Mr Kursawe said.
Motorists are advised to avoid the area because of smoke and delays.
Grassfires are also burning in the west and the north of NSW, with the RFS advising residents in areas including Bourke, Coffs
Harbour and Singleton to prepare their properties. But no homes are under immediate threat.
Meanwhile, in inner western Sydney, a home in Empire Avenue, Concord, was destroyed by fire after midday today.